Yep, I could have used a rust converter and painted it internally, but I felt like the access was difficult and that process was more labour intensive.
The fish oil was one application.
The welder I bought was a CIGWELD EasyWeld 160 MIG/stick inverter welder.
I used the gasless MIG to weld this.
I think the unit is really aimed at beginners as it's very easy to set up. It has a digital display and you set the wire thickness, and metal thickness and the amps are preprogrammed, but you can adjust and fine tune the settings as you gain experience.
You can also use it with gas too.